Patients with end-stage renal disease (ESRD), including those patients already on either hemo- or peritoneal dialysis, have a multitude of metabolic abnormalities secondary to the diseased and nonfunctioning kidney. Secondary hyperprathyroidism is characterized by high levels of parathyroid hormone (PTH), a substance that is responsible for calicum/phosphorus balance in the body. In ESRD patients, current therapy for secondary hyperparathyroidism involves the use of dietary restriction of phosphorus oral or intravenous analogs of vitamin D that act to suppress PTH levels, and phosphate binders to lower serum phosphorus. However, current therapy is limited due to noncompliance with phosphate binders due to frequency of dosing and its poor palatability with meals, and hypercalcemia with vitamin D therapy. Thus, many patients have progressive secondary hyperparathyroidsim. The most serious consequence of secondary hyperparathyroidism is high-turnover bone disease, as well as widespread calcium deposition throughout the blood vessels and soft tissues in the body. In addition, ESRD patients with elevated PTH levels are prone to severe itching, bone pain secondary to bone turnover or fractures. If symptoms persist despite attempts at medical therapy, the current standard of care is to perform a surgical parathyroidectomy. Unfortunately, as with all surgeries, there can be significant morbidity and rarely mortality associated with this procedure. AMG 073 is a new drug, that can serve as a medical alternative to surgical parathroidectomy. AMG 073 will reduce the levels of parathyroid hormone by mimicking the effects of serum calcium by binding to the calcium receptor of the parathyroid cell, and decrease the release of parathyroid hormone. This is a phase II multi-center trial to determine safety and efficacy of AMG073 in hemodialysis patients with secondary hyperparathroidism.